Nakipagtalik po ako Nong SEP 2 and 7 then nag PT Ako Nong SEP 20 kailan po possible na nabuo Yun?

Congrats, mama! Based on your dates, most likely nabuo siya around late September, probably around Sep 16-21 area since pregnancy usually starts counting from your last period (which we don't know exactly, pero typically conception happens around ovulation time). Pero honestly, ang exact timing ay mahirap i-pinpoint without knowing your cycle, better to ask your OB when you go for your first ultrasound, sila na mag-confirm based sa baby's size!